This invention relates to a copper alloy suited for use as a lead material for semiconductor devices, such as transistors and integrated circuits (IC).
Heretofore, high nickel alloys, e.g., Kovar (Fe-29Ni-16Co) and 42 alloy (Fe-42Ni), have been adopted by preference as lead materials for semiconductor devices, because of their low thermal expansion coefficients and good bonding and sealing properties when joined to the semiconductive elements and moldings. In recent years, with the development of semiconductor circuits with increased degrees of integration, there has been a growth in the percentage of IC's of high power consumption types employed. Accordingly, lead materials made of the copper-base alloys that rapidly dissipate heat or exhibit good thermal conductivity have found usage. Today, such copper-base alloys as oxygen-free copper, phosphor bronze, tin brass, and red brass are in use. However, none of those copper-base alloys have been found to possess all the varied properties required as a lead material, i.e., good heat dissipation, thermal resistance, solderability, plating adhesion, repeated bending strength, and inexpensiveness.
For example, oxygen-free copper is of highly heat-dissipating ability but its heat resistance and strengths are insufficient. Phosphor bronze has outstanding strength but is costly and is itself a poor heat radiator. Tin brass is yet to be improved in heat resistance, although the other properties are excellent. Since it uses the expensive tin as the addition element, the adoption of some other less expensive alloys instead is being called for. Red brass is available at low cost and is useful as a multipurpose material but has a disadvantage of low heat resistance. With the merits and demerits the conventional copper-base alloys have not necessarily been satisfactory from the overall viewpoint for the applications as lead materials.